Friction element and process of producing same



Patented Nov. 20, 1928.

UNITED STATES PATENT o l-Flee.

IZADOR J. NOVAK, OF BRIDGEPORT, CONNECTICUT, ASSIGNOR TO RAY BESTOS COM- PANY, OF BBIDGEPORT. CONNECTICUT, A CORPORATION OF CONNECTICUT.

FRICTION ELEMENT AND PROCESS OF PRODUCING SAME.

No Drawing. Application filed' February 26, 1923, Serial No. 621,487. Renewcd'Decembcr 25!, 1927.

This invention relates to improvements in friction elements and process of producing same and refers more particularly to the binder substance used in connection with the production of friction elements such as brake linings, clutch facings, and other products of a like character.

Friction elements generally used at the present time are usually made up of an asbestos fabric or fibrous massimpregnated w1th asphalt, drying oils, rubber or resins, elther alone or in combination. These saturants comprise the large proportion of frict on ma terials used. Generally these materials require the use of some organic solvent as a carrier or vehicle utilized to impregnate the asbestos fabric or fibre with the b nder or saturant. This carrier may be gasol1ne,benzol, or

other solvents of a somewhat similar charac-.

ter. Rubber friction elements may onmay not be made with the use of a solvent.

The use of an organic solvent such as those mentioned is always attended, however, by at least two disadvantages: First, the high fire risk, and, second, the loss, either partial or complete,-of the expensive solvent. It has therefore been of the utmost importance to find a. binder or saturant for friction elements which could be incorporated into the asbestos fibre with a cheap solvent such as water as a carrier. Such a saturant has been found in the dried waste sulphite liquor such as that which is a waste product from paper pulp mills.

This waste sulphite liquor is produced in extremely large quantities by chemical pulp mills using the so-called sulphite process. as

' a waste product of the separation of'the cellulose or fibre from the wood. It is understood to contain as its principal c onstituentsthe' calcium salts of the lignin-sulphonic acids, and sugars formed in thefdeoomposition, or present in the sap. It has excellent adhesive properties and is perfectly miscible with water in all proportions. It does not melt under heat, but carbonizes and hardens.

Upon incorporation into the asbestos woven stock for use as brake lining, this material when present to the extent of 15% more or less of the total weight gives a hard wearresisting friction material with a remarkably uniform co-eflicient of friction averaging about .33. When used on an automobile in actual service it will give a very effective braking action, smooth and positive under all cond1t1ons of temperature obtained 1n service tests.

The method of producing a friction material from the woven asbestos tapesuch as is generally used for the manufacture of brake lining consists merely in completely saturating the raw tape in'the waste sulphite liquor containing that proportion of solids to water which is found to give the most satisfactory proportion of saturant to thefinished tape. This latter proportion has been found to. lie between ten per cent (10%) and twenty per cent (20%), although percentages above and results are obtained by the" incorporation of this binder'in woven clutch facings the method of saturation being identical wlth that of brake linings. In the case of woven facings it has-been noted that the addition of a small amount of molasses,- dextrin or several other water-soluble adhesive materials u to about twenty per cent (20%) of the solids in the saturant improves the uniformity of the frictional co-eflicient considerably. Too lar e an excess of these water-soluble gums is un esirable. from the standpoint of resistance to wear.

The saturant may be used as a binder in the case of un-woven'clutch facings or brake linings which are made from felted asbestos mill board by cutting out the shape desired, saturatingvwith a bindin material, curing until sufiiciently hard and finishing to size. Particular care must be taken, however, to preserve the form of this type of friction element base, as there is a marked swelling and softening action in the presence of water. Once the material is dry, however, the sha e is firmly set by the hard, strong binder. T e same high frictional characteristics previously mentioned are also inherent in this type of friction facing. In addition to its use with felted and woven asbestos, friction elements made from wire tape covered with woven asbestos fibre may also be treated in a like manner.

By the use of waste sulphite liquor in various dilutions or concentrations, it has been possible to obtain a stron binder of easily variable hardness which Is adaptable to a large variety of friction elements substituting for the highly inflammable and costly carriers or solvents now used a non-inflammable and cheap one such as the Water of the sulphite liquor. The process also eliminates curing asin-the case of the drying oils, linseed or asphalt, and vulcanization in the case of rubber binders. It also provides a new use for a waste product, besides providing a very cheap and efiicient binder for a frictional material.

Iclaim as my invention:

1. A friction element having an asbestos base containing as a binder the solid residue of waste sulphite liquor produced by drying of the liquor.

2. Woven asbestos'covered wire tape containing. as a binder the solid residue from waste sulphite liquor produced by drying of the liquor.

3. In friction elements, the combination with an incombustible fibrous base, of a binder substance containing the solid residue from waste sulphite liquor produced by drying of the li uor.

4. In friction elements, the combination with a fibrous base, of a binder substance impregnated therein comprising a major portion of the solid residue from waste sulphite liquor and a minor portion of a water soluble adhesive gum in predetermined proportions produced by drying of the mixture.- 7

5. In friction elements, the combination with a fibrous base, of a binder substance comprising a major portion of thesolid residue from waste sulphite liquor and a minor portion of a water soluble gum.

6. A process of producing friction elements, consisting in impre nating an incombustible fibrous base wit waste sulphite liquor extended in water, and heat treating the saturated base to remove the water.

7. A process of producing friction elements, consisting in impregnatin a fibrous base with a mixture of waste sulp ite liquor and a Water soluble gum in relatively smaller proportions to the waste sulphite liquor, the saturating mixture being extended in water, and heat treating the saturated base to remove the water.

IZADOR J. NOVAK. 

